Method of making a wrought iron product



Aug. 17, 1954 V STORY 2,686,742

METHOD OF MAKING A WROUGHT IRON PRODUCT Filed Api'il 20, 1953 M INVENTOREDWARD B. STORY They are relatively long ample, 2000 F. The heattreatment coalesces or nodulizes the slag masses formed by fracturing ofthe original long stringy slag fibers. Those masses assume generallyround or spherical shape as shown in both Figure 3 and Figure 5 but moreclearly in the latter figure. The slag nodules are designated byreference numeral 3 in Figures 3 and 5. Figure 5 shows the result ofheat treating at a temperature above 1900 F. of wrought iron as shown inFigure 4. The generally rectangular or block-like slag masses co-.alesceor nodulize into masses which are more stringy masses of slagwhose shape comes about through hot rolling of the wrought iron. The

slag masses of Figure 1 are not fragmented or fractured; in some casesthey are necked off by the hot rolling, i. e., by being rolled so thin-1 that they separate while still plastic into individual aligned longstringy fibers.

To show more clearly the character of the slag fibers in conventionallyrolled wrought iron I have provided Figure 2 which, as above stated, isa photomicrograph at one thousand magnifications' of a section ofconventionally rolled wrought iron, the section being taken parallel tothe direction of rolling. The slag fibers are indicated by referencenumeral 2 in Figure 2. They are long stringy slag masses orientedgenerally parallel to the direction of rolling. The long stringy slagfibers considerably reduce the transverse tensile strength and ductilityof the wrought iron. conventionally unidirectionally rolled wrought ironshows a ductility or elongation of about 5% or less in a transversetension test. The best transverse ductility of conventionallyunidirectionally rolled wrought iron is less than 7%.

Figure 3 is a photomicrograph at one hundre magnifications of a sectionof wrought iron made in accordance with my improved method, the wroughtiron having been annealed at a temperature above the temperature atwhich the slag inclusions lose their plasticity, the section being takenparallel to the direction of rolling. The reduction of the wrought ironshown in Figure 3. has been effected largely at temperatures below thetemperature at which the slag fibers lose their plasticity, to wit,largely below 1900 F. The rolling fractures or fragments the elongatedslag fibers into a series of slag masses which are aligned in thedirection of rolling. A single long stringy slag fiber existing at 1900F. may fracture into a large number of aligned masses as the rollingcontinues below 1900 F.

Figure 4 is a photomicrograph at one thousand magnifications of asection of wrought iron made in accordance with my improved method abovedescribed except that the wrought iron shown was not annealed at atemperature above the temperature at which the slag inclusions losetheir plasticity, the section being taken parallel to the direction ofrolling. The fractured slag masses are clearly shown in Figure 4 butthey assume a shape which is more rectangular or block-like in crosssection than spherical. They are designated by reference numeral 4.

Figure 5 is a photomicrograph at one thouand magnifications of a sectionof wrought iron as shown in Figure 3 clearly illustrating the separatealigned slag masses formed by fracturing non-plastic long stringy slagfibers. The wrought iron shown in Figures 3 and 5 has been heat treatedat a temperature above the temperature at which the slag inclusions losetheir plasticity, i. e., at a temperature above 1900 F., for exnearlyspherical in shape. The coalescing or nodulizing' of the slag fibers isaccompanied by some increase in the spaces therebetween with aconsequent increase in transverse ductility of the wrought iron.

The transverse ductility of wrought iron made by my improved process ismuch higher than the transverse ductility of conventionallyunidirectionally rolled wrought iron and-may be several times as great.A typical specimen of wrought iron as shownin Figure 3 displays atransverse elongation of about 17% or. in the neighborhood of threetimes the transverse elongation of very good conventionallyunidirectionally rolled wrought iron. My improved wrought iron shows atransverse elongation of a minimum of about 7% which is better than thebest trans verse elongation of conventionally unidirection ally rolledwrought iron. The ductilities are measured by the percentage elongationin a standard tension test in'a gauge length of 8" of a transverse testspecimen of normal cross section. The cross-sectional dimensions of thetest specimen may, for example, be of the order of 1.5" x .1". I

While I greatly improve the transverse properties of wrought iron thelongitudinal properties remain approximately the same as thelongitudinal properties of conventionally unidirectionally rolledwrought iron. Thusmy wrought iron suffers nothing inlongitudinalproperties while being improved as much as threefold in transverseproperties.

In a preferred method of procedure I may heat a wrought iron'billet toabout 2500 F. and roll the billet until the temperature of the wroughtiron has fallen to a temperature substantially lower than 1900 F. Afterthe wrought iron cools below 1900 F. the slag inclusions lose theirplasticity and upon further rolling they are fractured or torn apart asabove described into masses each having a dimension in the direction ofalignment equal to a minor fraction of the length of the original fiber.The slag masses are aligned in the direction of rolling and in thedirection of the length of the original fibers. They are of generallyblock-like appearance in a cross section taken parallel to the directionof rolling as shown in Figure 4. As indicated above, if the rolling iseffected at temperatures only slightly lower than 1900 F. the rolling isdesirably continued until the thickness of the wrought iron is notsubstantially greater than one-half of the thickness of the wrought ironat the beginning of the portion of the rolling following cooling of thewrought iron to 1900 F. which insures fragmentation of a substantialnumber of slag fibers. As already explained, the extent of rolling orother working to accomplish the desired fragmentation of the sla fibersmay be substantially reduced as the temperature is reduced. The thusrolled wrought iron is annealed by heating it to 1900 F. or some-.

what higher to cause the slag fragments to coalesce with the advantagesabove explained.

By my invention I can produce by unidirectional rolling withoutreheating wrought iron whose transverse ductility is far greater thanthe transverse ductility of conventionally unidirectionally rolledwrought iron and at leastas high as the ductility in either crosswisedirection of cross rolled wrought iron whose ductility in bothdirections of rolling at right angles to each other is about the same.The longitudinal ductility of my improved wrought iron is very muchgreater than the ductility in the respective directions of rolling ofcross rolled wrought iron and is at least equal to the longitudinalductility of most conventionally unidirectionally rolled wrought iron.The rolled product may be of any desired length, no limit being imposedon its length except by the size of billet which can be produced androlled.

The improved product of my invention has many uses and is of wideutility. As an example, it is ideally suited for heat exchanger pipewhich is thin walled tubing whose ends pass through holes in tube sheetsand are rolled back against the sheets. When my improved method isemployed in making the wrought iron heat exchanger tubing of any desiredlength may be produced and may be rolled over against the tube sheetWithout danger of splitting.

While I have shown and described a present preferred method ofpracticing my invention it is to be distinctly understood that theinvention is not limited thereto but may be otherwise variouslypracticed within the scope of the following claims.

I claim:

1. A method of making a wrought iron product out of wrought iron havingelongated slag fibers comprising fragmenting the elongated slag fibersby working the wrought iron at a temperature 6 below 1900 F. andthereafter coalescing the fragmented slag fibers by annealing thewrought iron at a temperature at least about 1900 F.

2. A method of making a rolled wrought iron product comprising rollingwrought iron generally parallel to an axis in the wrought iron and whilethe wrought iron is at a temperature below 1900 F., continuing saidrolling until slag fibers of the wrought iron fragment and thereaftercoalescing the fragmented slag fibers by annealing the wrought iron at atemperature at least about 1900 F. l

3. A method of makin a rolled wrought iron product comprising rollingwrought iron generally parallel to an axis in the wrought iron andvwhile the wrought iron is at room temperature,

continuing said rolling until the thickness of the wrought iron has beenreduced about 10% and annealing the wrought iron at a temperature atReferences Cited in the file of this patent UNITED STATES PATENTS NumberName Date Re. 7,003 Lauth Mar. 21, 1876 826 Johnson July 9, 18382,335,506 Grange Nov. 30, 1946 OTHER REFERENCES The Making, Shaping andTreating of Steel, publ. by U. S. Steel Corp, 1940, pages 310, 311, 327.

1. A METHOD OF MAKING A WROUGHT IRON PRODUCT OUT OF WROUGHT IRON HAVINGELONGATED SLAG FIBERS COMPRISING FREGMENTING THE ELONAGTED SLAG FIBERSBY WORKING THE WROUGHT IRON AT A TEMPERATURE BELOW 1900* F. ANDTHEREAFTER COALESCING THE FRAGMENTED SLAG FIBERS BY ANNEALING THEWROUGHT IRON AT A TEMPERATURE AT LEAST ABOUT 1900* F.